The purpose of this study is to investigate: 1) the effects of various dietary treatments on disease progression in the glycogen storage diseases (GSD); 2) the molecular basis and genotype-phenotype correlation of glycogen storage disease; and 3) the mechanism and treatment of renal disease associated with type I GSD. Patients are seen at 3 months and 6-month intervals for diet evaluation, anthropomorphic measurements and serum chemistries. Muscle strength is evaluated by formal muscle testing including Cybex, by EMG and by changes in serum enzymes 9CPK, LDH and isoenzymes, SGOT, SGPT). Renal function clearances and factors affecting hyperfiltration are monitored with diet intervention. Changes in size and number of hepatic adenomas are evaluated at 6-month interval by ultrasound and CT. Alpha 1-Fetoprotein is determined every 6 months in patients with adenomas. Skin fibroblasts and lymphoblastoid cells are obtained from GSD patients for analysis of enzyme activity, antibody-reactive materials, and DNA mutations.